Method for fabricating buried bit line in semiconductor device

Abstract

A method for fabricating a buried bit line in a semiconductor device includes forming a liner oxide layer over the entire surface of a substrate having bodies isolated by a trench, selectively etching the liner oxide layer contacted with one side surface of the trench to a given depth, forming a sacrifice layer at a larger height than an etched surface of the liner oxide layer wherein the sacrifice layer partially fills the trench to the larger height, forming a liner nitride layer on sidewalls of the trench over the sacrifice layer, removing the sacrifice layer to expose a part of a body at the one side surface of the trench, forming a barrier layer along the entire surface of the resultant structure including the liner oxide layer, and forming a buried bit line over the barrier layer to be contacted with the exposed part of the body.

1 . A method for fabricating a buried bit line in a semiconductor device, comprising:
 forming a liner oxide layer over the entire surface of a substrate having bodies isolated by a trench;   selectively etching the liner oxide layer contacted with one side surface of the trench to a given depth;   forming a sacrifice layer at a larger height than an etched surface of the liner oxide layer wherein the sacrifice layer partially fills the trench to the larger height;   forming a liner nitride layer on sidewalls of the trench over the sacrifice layer;   removing the sacrifice layer to expose a part of a body at the one side surface of the trench;   forming a barrier layer along the entire surface of the resultant structure including the liner oxide layer; and   forming a buried bit line over the barrier layer to be contacted with the exposed part of the body.   
     
     
         2 . The method of  claim 1 , wherein the forming of the sacrifice layer comprises:
 coating the liner oxide layer with a photoresist layer to fill the trench;   performing blanket exposure on the photoresist layer; and   developing the exposed part of the photoresist layer.   
     
     
         3 . The method of  claim 1 , further comprising slimming the liner oxide layer over the sacrifice layer, before the forming of the liner nitride layer. 
     
     
         4 . The method of  claim 3 , wherein the slimming of the liner oxide layer is performed by wet etching. 
     
     
         5 . The method of  claim 1 , wherein the forming of the liner nitride layer comprises:
 forming a liner nitride layer over the entire surface of the substrate including the liner oxide layer; and   etching the liner nitride layer to remain on the sidewalls of the trench.   
     
     
         6 . The method of  claim 1 , wherein the etching of the liner oxide layer comprises:
 forming a gap-fill layer over the liner oxide layer such that the gap-fill layer fills the trench;   forming a mask pattern over the gap-fill layer; and   selectively etching the liner oxide layer at one sidewall of the trench using the mask pattern.   
     
     
         7 . The method of  claim 1 , wherein the barrier layer comprises a stacked structure of titanium and titanium nitride. 
     
     
         8 . The method of  claim 8 , further comprising forming metal silicide at the exposed part of the body, before the forming of the buried bit line. 
     
     
         9 . The method of  claim 8 , wherein, in the forming of the metal silicide, a heat treatment is performed to cause the exposed part of the body and the barrier layer to react with each other. 
     
     
         10 . The method of  claim 8 , wherein the metal silicide comprises titanium silicide. 
     
     
         11 . The method of  claim 11 , wherein the forming of the buried bit line comprises:
 forming a polysilicon layer over the barrier layer such that the polysilicon layer fills the trench; and   etching the polysilicon layer to fill a part of the trench.   
     
     
         12 . A method for fabricating a buried bit line in a semiconductor device, comprising:
 forming a liner oxide layer over the entire surface of a substrate having bodies isolated by a trench;   selectively etching the liner oxide layer contacted with one side surface of the trench to have a first given height from the bottom of the trench;   forming a liner nitride layer on sidewalls of the trench, wherein the liner nitride layer is formed over a second given height of the trench and the second height is larger than the first given height to expose a part of a body at the one side surface of the trench; and   forming the buried bit line over a barrier layer to be contacted with the exposed part of the body.   
     
     
         13 . The method of  claim 12 , wherein the forming of the liner nitride layer comprises:
 forming a sacrifice layer by partially filling the trench to the second given height;   forming a liner nitride layer on sidewalls of the trench over the sacrifice layer; and   removing the sacrifice layer to expose the part of the body at the one side surface of the trench.   
     
     
         14 . The method of  claim 12 , wherein the forming of the buried bit line over the barrier layer comprises:
 forming a barrier layer along the entire surface of the resultant structure including the liner oxide layer; and   forming a buried bit line over the barrier layer to be contacted with the exposed part of the body.   
     
     
         15 . The method of  claim 13 , wherein the forming of the liner nitride layer comprises slimming the liner oxide layer over the sacrifice layer, before the forming of the liner nitride layer.